In recent years, as a device (also called a surface light emission device) for performing surface light emission which causes reduced power consumption, a light-emitting device (also called an organic EL device) that utilizes an organic EL (organic electroluminescence) is attracting attention, and its application to an illumination device, or the like, is in progress.
The organic EL device includes a structure in which an organic light emission layer is interposed between two electrodes (an anode electrode and a cathode electrode). As the area of the organic EL device increases, the likelihood of causing non-uniformity in the thickness of the organic light emission layer during a manufacturing process, or the like, increases. As a result, when the organic EL device emits light, non-uniform luminance, or the like, is exhibited, which may undesirably make a user perceive unevenness in the light emission (also referred to as uneven light emission). Such uneven light emission may also occur due to degradation of the organic light emission layer, or the like, that is caused in accordance with conditions under which the organic EL device is used.
Here, the organic EL device fulfills functions required as an illumination device, as long as a variation in the luminance during light emission falls within a predetermined range. However, if the user perceives a certain level of uneven light emission due to the variation in the luminance, the quality level of the organic EL device as an illumination device is impaired.
Therefore, for preventing occurrence of the uneven light emission, techniques for forming an organic light emission layer with a uniform film thickness have been proposed (for example, Japanese Patent Application Laid-Open No. 2009-245777)